One type of conventional conveyor has an upwardly facing surface which can slidably support articles to be conveyed, and has a plurality of pushing assemblies at spaced locations along an endless chain, each pushing assembly moving horizontally above the surface along one reach of the chain and having a plurality of rigid, downwardly projecting fingers which can engage the article and slide it along the surface. The article is located between two guide rails, and the distance between the guide rails can be adjusted to accommodate articles of different sizes. When the distance between the guide rails is increased or decreased, different pushing assemblies having a different effective width are used. In particular, every pushing assembly on the endless chain is manually removed from the chain and is replaced with a similar pushing assembly of larger or smaller effective width. Since this conventional type of machine typically has 10 to 15 pushing assemblies on the chain, is a relatively tedious and time consuming task to effect such a change in the configuration of the machine.
The assignee of the present invention has already developed an improved conveyor, which is disclosed in U.S. Ser. No. 07/789,415, filed Nov. 1, 1991, now U.S. Pat. No. 5,137,140. This improved conveyor has pushing assemblies with effective widths which are adjustable, and has an arrangement responsive to movement of the guide rails for automatically effecting adjustment of the effective widths of the pushing assemblies. This existing conveyor has been very advantageous in practice. However, while the particular mechanism provided in this existing conveyor to adjust the effective widths of the pushing assemblies is highly satisfactory for certain types of conveyors, there are other types of conveyors for which it is less satisfactory.
Accordingly, an object of the present invention is to provide an improved version of the pushing assemblies with adjustable widths and the mechanism which adjusts the widths of the pushing assemblies, for use in conveyors in which the mechanism disclosed in the prior application is less practical.